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Nancy Segal — Deliberately Divided: Inside the Controversial Study of Twins and Triplets Adopted Apart

Deliberately Divided: Inside the Controversial Study of Twins and Triplets Adopted Apart (book cover)

In the early 1960s, the head of a prominent New York City Child Development Center and a psychiatrist from Columbia University launched a study designed to track the development of twins and triplets given up for adoption and raised by different families. The controversial and disturbing catch? None of the adoptive parents had been told that they were raising a twin — the study’s investigators insisted that the separation be kept secret.

In this conversation based on her new book, Deliberately Divided: Inside the Controversial Study of Twins and Triplets Adopted Apart, Nancy Segal reveals the inside stories of the agency that separated the twins, and the collaborating psychiatrists who, along with their cadre of colleagues, observed the twins until they turned twelve. This study, far outside the mainstream of scientific twin research, was not widely known to scholars or the general public until it caught the attention of documentary filmmakers whose recent films, Three Identical Strangers and The Twinning Reaction, left viewers shocked, angered, saddened and wanting to know more. Interviews with colleagues, friends and family members of the agency’s psychiatric consultant and the study’s principal investigator, as well as a former agency administrator, research assistants, journalists, ethicists, attorneys, and — most importantly — the twins and their families who were unwitting participants in this controversial study, are riveting. Through records, letters and other documents, Segal further discloses the investigators’ attempts to engage other agencies in separating twins, their efforts to avoid media exposure, their worries over informed consent issues in the 1970s and the steps taken toward avoiding lawsuits while hoping to enjoy the fruits of publication. Segal’s spellbinding stories of the twins’ separation, loss and reunion offers readers the behind-the-scenes details that, until now, have been lost to the archives of history.

Nancy Segal, Ph.D. (CA), is a professor in the Department of Psychology at California State University, Fullerton, and the director of the Twin Studies Center, which she founded in 1991. She is the author of six books on twins including (most recent ones first): Accidental Brothers: The Story of Twins Exchanged at Birth and the Power of Nature and Nurture; Twin Mythconceptions: False Beliefs, Fables, and Facts About Twins; Born Together—Reared Apart: The Landmark Minnesota Twin Study; Indivisible by Two: Lives of Extraordinary Twins and Entwined Lives: Twins and What They Tell Us About Human Behavior, and the senior editor of Uniting Psychology and Biology: Integrative Perspectives on Human Development. She is also an associate editor of Twin Research and Human Genetics, the official journal of the International Society for Twin Studies. Dr. Segal’s media appearances include Today, Good Morning America, 20/20, the Oprah Winfrey Show, the Martha Stewart Show, Discovery Health, and the Diane Rehm Show on NPR.

Shermer and Segal discuss:

  • her historical interest in twins research and behavior genetics,
  • the many different types of twins and family arrangements,
  • a brief history of twins research:

    • Francis Galton,
    • William Blatz,
    • Josef Mengele,
    • conjoined twins Masha and Dasha Krivoshlypova in 1950’s Russia,
    • John Money’s attempt to turn an accidentally castrated male twin into a female,
    • Minnesota Study of Twins Reared Apart: Tom Bouchard, Nancy Segal,
    • Jack and Oskar, Jim Lewis and Jim Springer, Barbara and Daphne,
    • Segal’s doctoral research on twin children and cooperation and competition,
  • twins separated accidentally (switched with an unrelated infant, switched with another twin),
  • twins separated intentionally (China’s one-child policy),
  • twins reunited,
  • the meaning of “heritability” and “genetic,”
  • the relative role of nature and nurture in how lives turn out,
  • What is the “nonshared environment”?
  • How many genes go into height, personality traits, intelligence, creativity?
  • epigenetics and gene expression,
  • Lawrence Wright’s New Yorker article on Peter Neubauer’s twin adoption study,
  • psychoanalyst and psychiatrist Dr. Peter B. Neubauer,
  • Dr. Viola Bernard,
  • Louise Wise Adoption Services in NYC,
  • Child Development Center Twin Study,
  • Jewish Board of Guardians (now the Jewish Board of Family and Children’s Services),
  • documentary films: The Twinning Reaction and Three Identical Strangers
  • twins Anne and Susan,
  • twins Melanie and Ellen,
  • twins Howard and Doug,
  • twins Paula and Elyse,
  • twins Paula and Marjorie,
  • twins Michele and Allison,
  • triplets Bob, Dave, Eddy and their psychiatric problems.

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This episode is sponsored by Wondrium:

Wondrium (sponsor)

This episode was released on November 9, 2021.


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